Radiation-stable and thermally stable oils



United States Patent Ofiice 3,109,815 Patented Nov. 5., 1963 3,109,815 RADiATKPN-STABLE AND THERMALLY STABLE OILS Russell A. Hunt, .lr., Grifiith, and Blanchard L. Michel, Munster, ind, assignors to Standard Oil Company,

Chicago, 111., a corporation of lndiana No Drawing. Filed July 30, 1958, Ser. No. 751,852 6 Claims. (Cl. 252-33) This invention relates to hydrocarbon oil compositions having improved stability in the presence of ionizing radiation and at elevated temperatures.

Many applications of atomic energy developments and ionizing radiation make use of a hydrocarbon oil stream in close proximity thereto. Many of such developments are processes in which, by reason of its proximity, the oil is subjected to ionizing radiation and also oftentimes subjeoted to elevated temperatures in the neighborhood of 300 or 400 F. and even higher. Under such conditions ordinary mineral oils decompose at various rates and form deposits on the surfaces with which they come in contact. For example, one application of atomic energy to the propulsion of aircraft visualizes auxiliary turbo jet engines. The fuel for such an engine is advantageously as resistant as possible to the effects of ionizing radiation and is stable to the elevated temperatures produced during the time in which atomic energy in one of its forms is employed to propel the aircraft. Lubricating oils and other oils employed in the aircraft should also be stable to elevated temperatures and ionizing radiation. If the turbine fuel is not especially thermally stable nor radiation stable, deposits form in the fuel heat exchangers, lines, and fuel filters become clogged. Early operational failure of the turbo jet engine to function may occur.

An object of the present invention is to provide hydrocarbon oil compositions which have improved stability when subjected to ionizing radiation. Another object is to provide hydrocarbon oil compositions having improved thermal stability. A further object is to provide a method for reducing deposits and minimizing filter clogging that occurs when hydrocarbon oils are subjected to ionizing radiation and elevated temperatures and thereafter filtered.

It has been found that hydrogenated mineral oils containing a small amount, such as less than 1%, of a dialkylbenzene sulfonate salt have greatly improved stability when subjected to ionizing radiation and/or elevated temperatures. Hydrogenated mineral oils containing hydrocarbons boiling in the range of 100 to 600 P. such as kerosene or other fuel oils, may be improved by this invention. Dialkylbenzene sulfonate salts such as the sodium salt of didodecylbenzene sulfonate and similar compounds are very effective for this purpose.

In order to have improved stability toward ionizing radiation and elevated temperatures, it is important that the mineral oil be hydrogenated. Hydrogenation renders it substantially free of any unsaturated hydrocarbons and also removes some impurities such as sulfur compounds, nitrogen compounds and the like. The hydrogenated mineral oil may contain components that boil Within the range of 100 to 600 F. Thus gasoline boiling range materials, kerosene and other fuel oils, and lubricating oils which have been hydrogenated are contemplated within the scope of this invention.

The dialkylbenzene sulfonate salt may be one such as didodecylbenzene sulfonate salt. The pure compound need not be employed, but impure mixtures thereof usually containing less than 25% or so of the monoalkylbenzene sulfonate salt may be used. Rather than employing one individual dialkylbenzene sulfonate salt, mixtures of various dialkylbenzene sulfonate salts containing different alkyl substituents attached to the benzene nucleus or containing difierent metal salts may be used. While the didodecylbenzene sulfonate salt is preferred, the alkyl substituents may generally contain from 6 to 16 carbon atoms. The metal neutralizing the sulfonic acid group is preferably sodium, but other alkali metals or alkali earth metals and even heavier metals may be attached to the sulfonic acid group. The dialkylbenzene sulfonate salt is present in the hydrogenated mineral oil in minor amounts, ordinarily up to about 1% by weight. Amounts of from 0.0001 to 1.0%, e.g. 0.01% will usually be suificient. Other additives may be present in the hydrogenated mineral oil if so desired.

Certain radiationthermal stability tests were carried out which demonstrate the properties and advantages for the compositions of this invention. A modified CF-R Fuel Coker was used for Federal Test Method Standard No. 791, Method 34-64. -In the test, the hydrocarbon oil is passed through a preheater (which would correspond to a heat exchanger for heating oil) and then the preheated oil is passed through a sintered steel filter (which would correspond to a turbine combustor nozzle). The test may be run under the influence of an intense gamma radiation field. The oil is passed once-through the system for a period of time of 300 minutes or until the pressure difierential across the filter reaches 25 in. Hg. Thereafter the apparatus is disassembled and the amount or intensity of the deposits as Well as the percentage of surface area of the preheater covered by deposits is visually estimated and reported in terms of a numerical code. The pressure drop across the filter at the end of the run is also measured and reported. In these tests, the following results were observed.

1 0=no deposits; 2=1ight deposits; 3=light tan deposits; 4=brown or darker deposits.

2 Percentage of surface area of preheater which is covered with deposits 3 Na sulfonate salt of a dialkylbenzene mixture containing about geigllglecylbenzene and 10% of other dialkylbenzenes and monoalkylben- It is quite evident that only the hydrogenated kerosene containing the salt of dialkylbenzene sulfonate eliminates the formation of deposits and totally prevents any pressure drop across the filter. This is evidence of its greatly improved thermal stability and improved resistance to the effects of ionizing radiation. Kerosene or even hydrogenated kerosene do not fulfill these requirements.

Thus having described the invention, what is claimed is:

l. A composition consisting essentially of a hydrogenated hydrocarbon oil containing from 0.0001 to about 1% by weight of a dialkylbenzene sulfonate salt.

2. The oil composition of claim 1 wherein the hydrogenaited oil contains kerosene boiling range hydrocarbons.

3. The oil composition of claim 1 wherein said dialkylbenzene sulfonate salt is the sodium salt of didodecylbenzene sulfonate.

4. A composition consisting essentially of hydrogenated kerosene containing from 0.0001 to about 1% by weight of the sodium salt of didodecylbenzene sulfonate.

5. A number of the group consisting of hydrogenated gasoline, hydrogenated kerosene, hydrogenated fuel oils,

3 and hydrogenated lubricating oils containing from 0.0001 to about 1% by weight of a sodium salt of a dialkylbenzene sulfonate wherein said alkyl groups each contain from 6 to 16 carbon atoms.

6. Hydrogenated kerosene containing from 0.0001 to about 1% by Weight of a member of the group consisting of alkali metal and alkaline earth metal salts of a dialkylbenzene sulfonate having from 6 to 16 carbon atoms per alkyl group.

References Cited in the file of this patent UNITED STATES PATENTS 2,527,987 Caron et a1 Oct. 31, 1950 2,626,207 Wies et a1. Jan. 20, 1953 2,743,223 McClinton et a1. Apr. 24, 1956 2,862,800 Can-trel et a1. Dec. 2, 1958 2,866,694 Glendenning et al Dec. 30, 1958 2,905,606 Long et a1. Sept. 22, 1959 FOREIGN PATENTS 46,893 Canada July 25, 1950 784,793 Great Britain Oct. 16, 1954 OTHER REFERENCES AEC Publication, KAPL-731, Apr. 2, 1952, Summary 10 of Avail-able Data on Radiation Damage to Various Non- Gen. Station, September 1955, p. 3.

Modern Plastics, May 1957, pp. 174 and 176. 

5. A NUMBER OF THE GROUP CONSISTING OF HYDROGENATED GASOLINE, HYDROGENATED KEROSENE, HYDROGENATED FUEL OILS, AND HYDROGENATED LUBRICATING OILS CONTAINING FROM 0.0001 TO ABOUT 1% BY WEIGHT OF A SODIUM SALT OF A DIALKYLBENZENE SULFONATE WHEREIN SAID ALKYL GROUPS EACH CONTAIN FROM 6 TO 16 CARBON ATOMS. 